(1) Field of the Invention
This invention pertains to the field of gas flow regulators in thermodynamic environmental testing devices. More particularly, this invention pertains to a gas flow regulator comprising a gas passage duct that can be axially repositioned and rotationally reoriented relative to a chamber wall for controlling the flow rate of gas into the interior volume of a thermodynamic environmental testing chamber for increasing the spatial uniformity of the rate of temperature change throughout test specimens tested in the chamber. The flow regulator of the invention provides a simplistic and cost effective means of regulating the gas flow rate though a test chamber wall by merely axially and rotationally reorienting a gas passage duct relative to the cavity wall.
(2) Description of the Related Art
Thermodynamic environmental testing devices are used in various industries, primarily for testing the fatigue properties of test specimens, and operate by cycling the temperature of such test specimens. Testing devices typically comprise a large thermodynamically insulated box-like unit having one or more doors that provide access to an internal testing chamber therein. Heating and cooling of test specimens placed within the testing chamber is achieved by supplying heated or cooled gas into the chamber through ports communicating with the chamber interior volume. Using liquid nitrogen for cooling and electric heating elements for heat, the temperature change rates of test specimens can exceed 70xc2x0 Celsius per minute.
During operation, the temperature of gas flowing into the testing chamber of a testing device is commonly controlled by an electronic control module. Among other things, such control modules typically allow control of the temperature change rates, the maximum and minimum testing chamber temperature, and the maximum and minimum temperature of gas being supplied into the testing chamber. This is done by programming the control module with specific temperature cycling parameters and by providing the control module with feedback of monitored testing chamber temperatures. Such control modules are also typically interfaced with heating, cooling, and blower systems for controlling such systems in an effort to achieve the programmed cycling parameters.
The heated or cooled gas is typically delivered into the testing chamber via a plenum having one or more ports communicating with the chamber interior. The ports often comprise flexible hosing which allow the heated or cooled gas to be delivered to various locations within the testing chamber to improve the performance and efficiency of the testing device.
Despite the ability to regulate the gas temperature and its overall flow rate into the testing chamber using prior art testing devices, it is difficult to achieve spatially uniform rates of temperature change throughout various test specimens or throughout portions of each test specimen. This is because various test specimens generally have various heat-sink properties and even a single test specimen can have different portions that require more or less total heat or cooling to achieve the same rate of temperature change as other portions thereof. Although directing the gas flow from each of the ports using flexible hoses helps reduce spatial variations of the rate of temperature change throughout the test specimens, the spatial variations of the rate of temperature change within the testing chambers of prior art testing devices is still problematic.
The present invention overcomes the disadvantages associated with prior art thermodynamic environmental testing devices by providing gas flow regulators capable of independently adjusting the gas flow rate of heating or cooling gas flowing through a plurality of supply ports from one or more plenums into a testing chamber. By allowing independent adjustment of the gas flow through the plurality of ports, the total amount of heating or cooling gas flowing into the testing chamber can be distributed in a manner that reduces spatial variations of temperature change rates throughout one or more test specimens. Furthermore, a unique gas flow regulator is employed that comprises a minimal number of components and that is capable of adjusting gas flow through a test chamber wall by merely adjusting its position and orientation relative to a portion of the cavity wall.
In its intended operative environment, the gas flow regulator of the invention is employed with a thermodynamic environmental testing chamber of the type described earlier. Apart from the presence of the novel gas flow regulator of the invention, the thermodynamic environmental testing chamber is constructed as any typical testing chamber.
The chamber has an exterior housing with an interior volume employed in testing specimens that are enclosed in the housing of the chamber. The housing includes one or more doors that provide access to the interior volume of the chamber. In addition, a plenum is provided inside the chamber housing. The plenum extends around opposite sides of the interior volume of the chamber and is supplied with a flow of gas from a source of the type described earlier. The gas flow through the plenum is either cooled or heated as desired for the particular test being conducted in the chamber. The plenum encloses a second, interior volume through which the gas flow passes. The second interior volume is enclosed by at least a first wall and a second wall of the plenum. The first wall of the plenum is provided with the supply ports that communicate the second volume of the plenum interior with the first volume of the chamber interior containing the test specimens.
As set forth above, the gas flow regulator of the invention is used in the typical thermodynamic environmental testing chamber described above in its preferred operative environment. However, it should be apparent that the simplistic construction and operation of the gas flow regulator of the invention may be employed in other similar environments where it is desired to provide a low cost and simple to operate regulator that adjusts the flow of gas from one volume on one side of a wall to another volume on an opposite side of the wall. To explain the construction and the operation of the gas flow regulator of the invention, the illustrative embodiment of the thermodynamic environmental testing chamber will be employed.
In the illustrative embodiment of the gas flow regulators, the gas flow supply ports in the plenum first wall separating the first volume of the test chamber interior from the second volume of the plenum interior are circular. The simplistic construction of each gas flow regulator is comprised of a cylindrical duct and a locking mechanism. The cylindrical duct has a selected length with opposite first and second ends. A cylindrical interior surface of the duct defines a passageway through the duct having a center axis. The exterior surface of the duct is cylindrical and has a circumferential dimension that matches the interior circumferential dimension of the holes of the ports in the first wall of the plenum so that the duct may be inserted into one of the holes in a tight friction fit. This enables the duct to slide within the hole while the edge of the plenum first wall around the hole provides support for the duct. The first end of the duct has an annular edge that lies in a plane perpendicular to the duct center axis. The opposite second end of the duct is beveled in shape. Preferably, the second end of the duct has an elliptically shaped edge that lies in a plane that is oriented obliquely to the duct center axis.
The gas flow regulator is assembled to the test chamber by the duct being inserted through one of the holes in the first wall of the plenum. The duct is positioned in the hole with the first end of the duct positioned in the first volume of the test chamber interior and the second end of the duct positioned in the second volume of the plenum interior. A gas flow regulator is assembled into each of the holes of the plenum ports.
The locking mechanism of the gas flow regulator is preferably an adjustable band clamp of the type known in the prior art. As in the typical band clamp, the band clamp of the regulator has opposite ends with slots formed across one end that function as rack teeth and a screw housing containing an adjustment screw at the opposite second end. The band first end is inserted through the screw housing forming the band in a loop, and on rotation of the screw in the screw housing the threads of the screw pass through slots of the band first end adjusting the size of the loop formed by the band.
The band of the locking mechanism is positioned over the exterior surface of the duct in the first volume of the test chamber interior where it is accessible from the test chamber. The screw housing of the locking mechanism is secured to the plenum first wall to hold the locking mechanism stationery relative to the first wall. By screwing the screw in the screw housing of the locking mechanism, the band is constricted around the duct and thereby holds the duct in a stationery position relative to the first wall of the plenum.
In the illustrative environment of the invention, a gas flow regulator is positioned in each hole in the air plenum first wall to regulate the flow of gas through the second volume of the plenum interior to the first volume of the test chamber interior.
In operation of the test chamber employing the flow regulator of the invention, the test chamber is activated causing a flow of gas (either heated or cooled) through the second volume of the plenum interior. It is typical that the flow of gas be directed in a single direction from the source of the gas flow toward the holes in the first wall of the plenum. The duct of the gas flow regulator positioned in each of the first wall holes channels the gas from the interior volume of the plenum through the passageway of the duct, and into the interior volume of the test chamber.
With the duct second end in the interior volume of the plenum having a beveled edge, rotating the duct in the plenum wall hole so that the elliptical opening of the beveled edge faces into the flow of gas through the plenum will result in a greater amount of the gas flow being channeled through the passageway of the duct and into the test chamber interior. Turning the duct 180 degrees in the plenum wall hole so the elliptical opening of the beveled edge faces away from the flow of gas will adjust the flow of gas through the passageway of the duct, decreasing the flow. In addition, with the interior volume of the plenum being defined between the first wall of the plenum that supports the gas flow regulator ducts and the second wall of the plenum that is positioned on the opposite side of the plenum interior volume from the first wall, moving each regulator duct axially so that the second end of the duct is spaced further away from the second wall of the plenum will increase the area between the duct second end and the plenum second wall and enhance the free flow of gas supplied through the plenum interior volume to the duct and through the duct passageway into the test chamber interior volume. Conversely, moving each duct axially through the hole of the plenum first wall toward the second wall of the plenum so that the duct second end is positioned closer to the plenum second wall decreases the area between the duct second end and the plenum second wall and restricts the free flow of gas supplied through the plenum to the duct and through the duct passageway into the test chamber interior volume.
Thus, by rotating each duct in its hole of the plenum first wall and by axially adjusting the position of each duct in its hole in the plenum first wall the rate of gas flow through each duct passageway from the plenum interior volume to the test chamber interior volume can be adjusted. When the desired rate of gas flow through each duct passageway is achieved, the duct can be held in its adjusted position by tightening the screw of the locking mechanism, thereby holding the duct stationery in its adjusted position relative to the plenum wall.
By providing a plurality of holes in the plenum first walls on the opposite sides of the test chamber interior volume and a plurality of gas flow regulators of the invention mounted in the holes, the flow of gas from the plenum interior volume into different portions of the test chamber interior volume can be adjusted, thereby achieving a means of obtaining a more spatially uniform rate of temperature change throughout various test specimens or throughout various portions of a test specimen positioned in the interior volume of the test chamber.